Ghosh and Jain (“An Algebra of Geometric Shapes”, IEEE Computer Graphics and Applications, 1993, 50) describe the use of Fast Fourier Transforms (FFTs) to model the outline of a shape by tracking around its outer periphery.
It is of considerable importance in biometric systems that rely on iris recognition to be able to identify and map accurately both the outer edge of the iris and also the inner edge (the periphery of the pupil). Many iris recognition systems assume that the shape of the pupil is always circular, an assumption which may be inaccurate in many cases. Indeed, even when pupils are circular, they tend to become elongate or oblong when viewed from an angle.
Some research into non-circular pupil localisation has been carried out: See B. Bonney, R. Ives, D. Etter, and D. Yingzi, “Iris pattern extraction using bit planes and standard deviations,” Conference Record of the Thirty-Eighth Asilomar Conference on Signals, Systems and Computers, 2004, Y. Du, B. L. Bonney, R. W. Ives, D. M. Etter, and R. Schultz, “Analysis of Partial Iris Recognition Using a 1-D Approach,” Proceedings of the 2005 IEEE International Conference on Acoustics, Speech, and Signal Processing, Mar. 18-23, 2005. However, in spite of these earlier approaches, there still remains a need for a system which can in a straightforward way approximate a boundary given a number of points (which may not be equally spaced) on that boundary.